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An environmental gradient change of Picea mongolica seedling from the center of a forest canopy gap in forest-steppe ecotone in Inner Mongolia Autonomous Region of China

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An environmental gradient change of Picea mongolica seedling from the center of a forest canopy gap in forest-steppe ecotone in Inner Mongolia Autonomous Region of China

    An environmental gradient change of Picea

    mongolica seedling from the center of a forest canopy gap in forest-steppe ecotone in Inner Mongolia Autonomous Region of

    China

    JournalofForestryResearch,l7(3):221-225(2006)

    AnenvironmentalgradientchangeofPiceamongolicaseedlingfromthe

    centerofaforestcanopygapinforest-steppeecotoneinInnerMongolia

    AutonomousRegionofChina

    ZOUChun-jing.,ZHANGChao2,MAYong-liang2,XUWenduo

    ShanghaiKeyLaboratoryofUrbanization&EcologicalRestoration,EastChinaNormalUniversity,SchoolofLlyeSciences

    Shanghai200062,PR.China

    EastChinaNormalUniversity,SchoolofResourcesandEnvironmentalSciences,Shanghai200062,R.China

    .InstituteofAppliedEcology,ChineseAcademyofSciences,Shenyang110016,PR.China Abstract:Insandyforestwithaforestcanopygapforaperiodofover30years,thespruce(Piceamongolica)seedlingsweremonitoredon

    two5-m

    widetransectsfromthecenterQfalargegapintothesurroundingforest.Thefarthertheyweretothefarcenter,etallergrewthe

    seedlingandthemoreisthenumberofseedling.Thereweremanyseedlingsunderthecanopybutalmostallseedlingsdiedbeforeev

    growup.Alongtheforestedge,growthofseedlingswastemporarilyenhancedbylateralpenetrationoflightfromthegap.Theimplications

fornaturalforestregenerationdynamicsarediscussed.OurresultsprovethatinPmongolicaf

    orestagapdisturbancecreatesanonuniform

    environmentforregenerationofthespecies,anddeterminesthattheforestwasanon

    evenagedforest.

    Keywords:Piceamongolica;Sandyforest;Seedfinggrowth;Canopygap;Photosyntheticall

    yactiveradiation;Soilmoisture

    CLCnumber:$753.3Documentcode:AArticleID:l007-662X(2006)03q)22l)5

    Introduction

    PiceamongolicaWD.Xuisanendemicandendangerspe

    ciesinInnerMongoliaAutonomousRegionofChina(Xueta1. 1994).Astoecosystem.thespruceforestlocatesattheecotone betweenforestzoneandsteppezone(Fig.11.Astocultivateway, theforestisintheecotonebetweenagriculturaldistrictandpas

    toralarea.TheareaisalsoatransitionalzonefromDaxing'an MountainstoHunshandakeSandyLand(Xueta1.1998).

    Fig.1Locationofthestudyarear2hmz)

    Disturbancesthatcreategapsofvarioussizesareacolninon featureoftheecologyofborealconiferousforests(Bergeronet a1.1998;Ollieta1.2003).Innaturalforests,minorperturbations suchasinsectdamageandtimberharvestingcreatingsmallgaps Foundationproject:TheNationalNaturalScienceFoundationofChina(No. 399o0019.30070129)

    Biography:ZOUChunjing(1968?),male,associateprofessorinShanghai KeyLaboratoryofUrbanization&EcologicalRestoration.EastChi/laNor- malUniversity,SchoolofLifcSciences.Shanghai2ooO62.P.R.China. Receiveddate:2o05.1O.18:Accepteddate:2o06.O2.14

    Responsibleeditor:ZhuHong

    aremorecommoninsandyforestinthenorthofChina(Zoueta1. 1998).Themeanareaofagapis0.1hrninPmongolicaforest. andtheguidelinesforpreservationofvaluablehabitatsincrease

thelengthoftheedgeconsiderably(Xueta1.1998).Gapdistur

    banceopensspaceandreleasesresourcesthatinitiatevegetation successionandfacilitatetreeregeneration(Bazzazeta1.1994; DeChantaleta1.2003:Kuuluvainen1994;Lertzman1992; McGuireeta1.2001:Lieta1.1997).Manyresearchesonvarious typesofforestshavefocusedontheeffectofgapsonplantsloe

    ciescomposition(Collinseta1.1988)onavallabilityofresources, particularlylight(Messiereta1.1995;Rockwayeta1.1998)and onmicroclimate(Cheneta1.1993.1995;Taneta1.2000).In smallergaps.mostofthegapareasarelikelyinfluencedinsome wayoranotherbythesurroundingforest.

    Gapassociateddynamicsofthetreeseedlingisconsideredas amajorfactorindeterminingthestructureofforestcanopy(Platt andStrong,1989).eimportanceofgapsinseedlingrecruit

    mentincreasesinoldgrowthforests.wherevariationintypesof disturbanceeventsleadstodiversityof'regenerationniches' (Grubb,1977;Drobyshev,1999).Themostprevalentparadigm offorestregenerationdynamicsisgapcentered.bothtemporal andspatial:seedlingsarereleasedfromshadesuppressionbygap creationanditiscompetitionbetweenthemthereafter,inthegap environment,whichdeterminesthefutureforestcomposition (Browneta1.19921.Itisfrequentlyproposedthatthesizeofa forestcanopygapexertsthemostimportantcontroloverthe relativecompetitiveStatuSofseedlings.Thesizeofacanopygap isthemaindeterminantofboththeamountandthedurationof isolation.whichpenetratestheforest.Itisknownthatspruce seedlingsinsandyforestdifferintheirgrowthresponseatdif- ferentlevelsofphotosyntheticallyactiveradiation(PAR).Gaps mayalsoalterthespatialpatterningoffineroots.soilnutrients andsoilmoisture(Joneseta1.2003;Wilczynskieta1.1993:IAu

    f.2002).Insandyforest,soilmoistureisakeyforseedling growthandsurvival:thereforethesoilmoisturewouldaffectthe numberandheightofspruceseedlinginthegap(Zoueta1. Nt

222ZOUChun-jingeta1.

    2001).Denslow(1980)hasarguedthataspeciesmayregenerate preferentiallybeneathacertainsizeofcanopygap,whichcreates optimumconditionsforitsgrowthsincespeciesspecializations bestowcompetitivesuperiorityinoneparticulargapsizebut involveadaptivecompromisesthatrestrictsuccessingapsof differingsize.Despiteconsiderableresearchefforttherehasbeen remarkablylittleexperimentalevidencetotestthishypothesisof nichedifferentiationalongagapsizecontinuumamongstsym

    patrictreeseedlings.

    Gapsalterthestructureofaforestandhavebeenshownto havenonuniformsoilandlightenvironments(Brandanieta1.. 1988;Brown1993;Liangeta1.2001).Thegapphaseregenera

    tionhypothesisneedstoincorporatetheimplicationsof withingapheterogeneityforcompetitionbetweenspecies (Brown1996).Tl1ispaperreportstheresultsofmeasurements about30_.years..oldwildseedlingsofPmongolicagrowingalong thetransectfromthecenterofagaDintothesurroundingsandy forestinBaiyinaobaoNatUralReserveofInnerMongolia AutonomousRegion.China.Theobjectiveofthestudywasto determinewhetherPmongolicawouldshowchangesinitsrela. tivecompetitivestatusalongthelightandsoilmoisturegradient fromthegapcentertosurrounding.

    Materialsandmethods

    Studysite

    'IlhestudywasconductedinBaiyinaobaoNaturalReserve (43o30._43.36'N,117~06'-117.16.E,and1420minaltitude1in theeastofInnerMongoliaAutonomousRegion.China.The climateisatypicaltemperatecontinentsteppetype. Themean

    annualtemperatureis1.4.C.Theannualaccumulatedtempera

    tureof>5.Cis1942.C(Xu1985).Themeanannualprecipita- tionis448.9millandthepotentialannualevaporationisl526 mil1.Itisatypicalsemiaridix:gioninthenorthofChina.The

    lenIgthofthefrost.freeseasonis65days.

    Sprucedominatedforestsgrowonmostoftheterritoryofthe reserve.Whilestandswithlittleportionsofbroadleavedspecies

    (mainlywithBetulaplatyphyllaSuk.,andPopulusdavidiana Dode.)occupylowerpartsofwell?drainedslopes.Themeanage 0fthestandwas1l0yearsandithad0riginatedbynaturalre. generation.Themeanheightoftreeswas17m.Thestandhad 950stems?hm.,andstemvolumewas450m.hm..Thezonal soilsoftheareaalemainlyblacksoilandbrownsoilondunes. whicharepodzolic,andtherealsoalemeadowsoil.marshsoil andsaltsoilonriverbanks,andmeadows.Thegroundwatertable isatadepthof5-8HLThemeanthicknessofthehumuslayer wasca.50mil1.TheshrublayermainlyconsistedofOstryops davidianaDecne.CotoneastermelanocarpusLodd.Dasiphora fruticosa(L.)Rydb.RosadavuricaPal1.Theherblayerconsisted mainlyofAneurolepidiumchinense(Trin.)Kitag.,Agropyron crtstatumGaertner.,Calamagrostisepigeios(L.)Roth..andAr. 2).Thegapisabout30yearsoldaccordingtoourinvestigation. andtherearealotofspruceseedlingsofvariousages. .罄爱务《一椎:礓嗲?{'《璧薛':

:?:辫盎

    01020304O5060T080

    Width(m)

    Fig?2Themapofthetreecrownsintheexperimentalareashowing thelocationofthegapedge

    (Thecircledenotesthegap,anddarkerdotsshowtheremaininglivingtrees. Thesizeofthedotisdirectlyrelatedtothewidthofthetreecrown) Studymethods

    widetransectswerelaidoutinnorthsouthand Two5m

    westeastdirections40mfromthecenterofagaDofapproxi

    mately45%canopyopenness,intothesurroundingclosedforest. TheexperimentalgapwaslocatedinBaiyinaobaoNaturalRe

    serveandhadacomparablemicroclimate.

    PARwasmeasured

    continuallywithanintegratingquantumsensoLataheightof0.5 m,foraperiodof2monthsinthegapcenterandevery5m alongthetransect.Soilmoisturewasmeasuredcontinuallyfora periodof2monthsinthegapcenterandevery5malongthe transects.

    PmongolicaforestinBaiyinaobaoNaturalReserveischarac

    terizedasapureforest.Pmongolicaisshadetolerantclimax

    sandyforesttreeandhighlyspecializedadaptationtogapmi

    cro-environment.Thegrowthandsurvivalofthespruceseed

    llngs/oundgrowingalongthesetransectsweremonitoredin 2000aftergapcreationforover30years.BothPARandsoil motstureavecomparedwiththosemadeintwonearbyclosed forestcontrolplotsof120mand240mlocatedatleast100m fromanycanopygap.

    Statisticalanalysis

    Theeffectsofsamplingyearandpositioninthegapandunder

    thecanopywereestimatedbymeansofANOVA.Thestatistical datawasanalyzedbyusingMicrosoftExcel2000.

    temisiafrigidaWiud"!as

    natedbyPhytidiumrugosum(HedwKindbsandPhytidiadphtreResllltS.).,"Pf^cs

    (Hedw.)Warnst.

    Experimentalarea

    memiddleofamaturePmongolicastand.anexperimental areaof80m×80mwassetup.Allfhefleesweremappedinthe experimentalareaandinitsclosevicinitybyusingatachymeter. themiddleofthearea,thereisacanopygap,anapproximate1v lsodiametricareaofl000mwithadiameterofabout36m(Fig. mPmongolicaforest,gapaltersthelightenvironmentsof variousplantspecies.InFig.3.averticalprojectionoftheedge 0fthecanopygapwouldfallatapproximatelyl5mfromthegap centeralongtransects.PARisnonuniformwithinthegap.In

    thisgapmeandailyPARreceiptsatthegapedgewereapproxi

    matelyhalfofthatatthecenter.Thereisapenumbralzone aroundthegap,whichalsoreceivesmorePARthantheclosed forest.MeandailyPARreceiptsatthepointsofuptol5mfrom ???们?加0

    JournalofForestryResearch,17(3):221-225(2006) thegapedgearesignificantlyhigherthanmeanPARreceipts measuredsimultaneouslyatfourpointsinclosedforestcontrol plots(p<0.05,Student'st-testforindependentsampleswithtin

    equalvariance).

    0.55.1010.1515.2020252530303535-40

    Distancefromthegapc~nter(m)

    Fig.3MeandailyPARreceiptsindifferentdirectionsof5-m-wide transectsfromthecenterofalargeforestcanopygapint0thesur-

roundingforest

    Inthegap,soilmoisturechangesalongtransectsduetothe shiftofPAR.h1g.4,thecurveshowsthemeansollmoisture alongtransectsfromgapcenterintothesurroundingforest.A horizontalchangeofsollmoistureistIlatsollmoistureincreases duetothereduceofPARreceiptsuDtOthegapedgefromout. wardtothegapcente~andtIlendecreasestoalowleveldueto theabsorptionbyrootsystemofPmongolicaundertheclosed forest.Soilmoistureisnonuniformwithinthegap.Inthisgap,

    meansol1moistureuDto15mfromthegapcenterweresignifi. cantlyhighermantIlosemeasuredsimultaneouslyatfourpoints inclosedforestcontrolplots,andmeansoilmoistureinsouth directionweresignificantlyhigherthantIloseinnorthdirection (p<0.05.Student'st-testforindependentsampleswithunequal variance).

    0.55.101015152O20.25253030.3535.40

    Distancefromthegapcenter(m)

    Fj4Mcansoilmoistureindifferentdirectionsof5.m-widetran- sectsfromthecenterofalargeforestcanopygapint0thesurround- ingforest

    Pmongolicaisshade.tolerantspecies.Therearemanyseed. 1ings(meanaboutl2/5m-)underthecanopv'andthereislittle variance.However,tIlevhavedifficultytogrowupbecauseof lowPARleve1.Alotofseedlingscomeintobeing.andalotof dieout.Oncetheseedlingshaveappropriateenvironment,they willgrowrapidly.InFig.5theseedlingdensityineachdirection oftransectsiscomparedwithtI1emeandensityofseedlings growinginclosedforestcontrolplots.TheclosertheyaretotIle gapcenter,thelesstheyare.Butontheedgeofgap,thereare moreandmoreseedlings.Significantdifferences(p<0.05,Stu.

    dent'st-testforindependentsampleswithunequalvariance)are W(1Ol5mand15-20m)andS(1O15mand15-20m).only

    thoseseedlings,whichweregrowingonthegapedgeweresig- nificanflydensertIlanthosefoundintIlecenterofgandunder

    closedforest.

    45

    40

    0-55-10101515.20202525.3030.3535-40

    Distancefromgapcenter(m)

    Fig.5Meanseedlingdensityindifferentdirectionsof5mwide transectsfromthecenterofalargeforestcanopygap-mt0thesur- roundingforest

    Errorbarsrepresentthe95%confidenceintervalaroundmeanvalues Seedlinggrowthofmongolica.includingheightgrowthis influencedbymanyenvironmentalfactors.suchaslight,tem- perature,sollmoisture,etc.Fig.6showsmeanchangesinseed. 1ingheightovertimeinthreesectionsoftransects.tIlegap,tIle gapedgeandclosedforest.Seedlingsinthegaphavegrownand continuetogrowataverylowratebecauseoflowsoilmoisture, stronglit,andhightemperature(themaximumis45.7Cin Julv).SeedlingsinclosedforestdosoduetolowPARreceipts. SeedlingSontheedgeoftIlegapshowedsignificantincreasein heiItforappropriatelightandsoilmoisture.Significantdi骶卜

    ences(p<0.05,Student'st-testforindependentsampleswith unequalvariance)areintIlewest(1015mand15-20m)and

    thesouthf10-15mand15-20m).Onlythoseseedlingswhich weregrowinginthegapedgeweresignificantlytallerthanthose foundinclosedforestandintIlecenterofthegap.

    3oo

    250

200

    8

    150

    100

    5O

    0

    0_55.1010.1515.2020.2525.3030.3535_40

    Distancefiomgapcenterfm)

    Fig.6Meanseedlingheightindifferentdirectionsof5-m-wide transectsfromthecenterofalargeforestcanopygapintothesur- roundingforest

    Errorbarsrepresentthe95%confidenceintervalaroundmeanvalues 如加mO

    u_Ej=一矗=IIuo?

    42O8642O

    一隹.0昌一《

    如加mO

    一一luolu0矗?一10?

JournalofForestryResearch,l7(3):221225(2006)

    52:107145.

    Jones,R.H.,Mitchell,R.J.,Stevens,G.N.,eta1.2003.Controlsoffineroot dynamicsacrossagradientofgapsizesinapinewoodland[JJ.Oeco/og/a, 134:132143.

    KuuluvainenT.1994.Gapdisturbance,groundmicrotopogmphy,andthe regenerationdynamicsofborealconiferousforestsinFinland:areviewJ.

    Ann.Zoo1.Fenn.,31:35-51.

    Lertzman,K.P.1992.Patternsofgap-phasereplacementinasubalpine,

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